Heat transfer apparatus and method

This application claims the benefit of U.S. Provisional Patent App. No. 63/355,449, filed Jun. 24, 2022; U.S. Provisional Patent App. No. 63/407,630, filed Sep. 17, 2022; and U.S. Provisional Patent App. No. 63/427,326, filed Nov. 22, 2022, which are all hereby incorporated by reference herein in their entireties.

This disclosure relates to systems for removing heat from a process fluid and, more specifically, relates to packaged cooling systems such as cooling towers.

Industrial cooling systems are used to remove heat from process fluid in various industrial processes, such as manufacturing processes, HVAC systems for buildings, and heat transfer systems for computer datacenters. One common approach for some industrial cooling systems is to have a heat exchanger, such as an air handler, in a building that transfers heat to a first process fluid (e.g., water or a water-glycol mixture) and a chiller in the building that removes heat from the first process fluid. The chiller transfers heat from the first process fluid to a second process fluid, which is routed to a heat rejection apparatus, such as cooling tower outside of the building. The cooling tower removes heat from the second process fluid and returns cooled second process fluid to the chiller. Chillers used in industrial cooling systems are typically quite large, with power ratings in the range of 100-300 horsepower being common.

An issue with operating an industrial cooling system year-round is that the cooling system is typically designed with sufficient maximum capacity to provide the required cooling even during the hottest days of the year. Providing sufficient maximum capacity for the hottest days of the year in traditional cooling systems involves utilizing higher-capacity system components, such as more powerful chillers, fan motors, pumps, etc. than are required for the rest of the year. The higher-capacity system components consume more energy and/or water than would lower-capacity components, but are used to provide sufficient maximum capacity for the cooling system.

Ice thermal storage systems are sometimes used with industrial cooling systems to provide extra cooling capacity at peak energy usage, such as in the afternoon of a sunny and humid summer day. Ice thermal storage systems have a thermal storage tank that is charged, e.g., ice in the tank is frozen, and discharged as needed to supplement the chiller and cooling tower of the cooling system. For example, the ice thermal storage system may operate to freeze water in the tank overnight when electricity may be less expensive from the local utility. The ice thermal storage system is discharged, e.g., the ice in the tank is melted by process fluid traveling through a coil in the ice tank, in the afternoon of the sunny and humid summer day to provide increased cooling capacity for the cooling system.

An issue with some cooling systems that utilize ice thermal storage is that the cooling system still relies on a large, e.g., 200+ horsepower, chiller in the building to chill water provided to the heat exchanger in the building. While providing sufficient maximum capacity, these large chillers often consume large amounts of energy even when the cooling capacity required is low. Another issue with some ice thermal storage cooling systems is that the one or more ice tanks may take up an entire room, or even a separate building, in order to provide adequate cooling capacity for a large-scale industrial cooling system. The size and complexity of large-scale ice thermal storage tanks may be impractical for some facilities. Further, ice thermal storage systems utilize glycol as process fluid which is more expensive than water, increases pumping power required to circulate the process fluid, and reduces heat transfer performance.

In one aspect of the present disclosure, a heat transfer apparatus is provided for an industrial process that requires process fluid at a process fluid set temperature. The heat transfer apparatus includes an air inlet, an air outlet, and a process fluid heat exchange circuit to receive process fluid from the industrial process at a temperature different than the process fluid set temperature and provide process fluid to the industrial process at the process fluid set temperature. The process fluid heat exchange circuit includes a heat exchanger, an airflow generator operable to cause air to travel from the air inlet to the air outlet and contact the heat exchanger, and a thermal energy storage.

The process fluid heat exchange circuit has a first mode wherein the process fluid bypasses the thermal energy storage and the heat exchanger transfers heat between the process fluid and the air. The process fluid may bypass the thermal energy storage by, for example, being routed around the thermal energy storage or being routed to the thermal energy storage when the thermal energy storage has limited heat exchange capability. As a further example, the process fluid may bypass the thermal energy storage when the process fluid is directed through the thermal energy storage but the phase change material has been drained from the thermal energy storage such that the process fluid leaves the thermal energy storage at substantially the same temperature as it entered the thermal energy storage. The process fluid heat exchange circuit has a second mode wherein the thermal energy storage transfers heat between the process fluid and the thermal energy storage and the heat exchanger transfers heat between the process fluid and the air. The heat transfer apparatus further comprises a controller operatively connected to the process fluid heat exchange circuit.

The controller is configured to operate the process fluid heat exchange circuit in the second mode based at least in part upon a parameter of the air and a determination of the process fluid heat exchange circuit in the first mode being unable to provide the process fluid at the process fluid set temperature. In this manner, the heat transfer apparatus may utilize the thermal energy storage to trim or partially satisfy the heat transfer load required to provide the process fluid at the process fluid set temperature. By selectively utilizing the thermal energy storage at peak heat transfer loads, such as on the hottest days of the year, the heat exchanger can be sized to have smaller capacity than if the heat exchanger were to satisfy the peak heat transfer load by itself, which facilitates the use of less water and/or energy by the heat exchanger during off-peak heat transfer load situations.

The present disclosure also provides a method for operating a heat transfer apparatus associated with an industrial process that requires process fluid at a process fluid set temperature. The heat transfer apparatus includes a process fluid heat exchange circuit for the process fluid that includes a heat exchanger, a fan to cause movement of air relative to the heat exchanger, and a thermal energy storage. The process fluid heat exchange circuit has a first mode wherein the process fluid bypasses the thermal energy storage and the heat exchanger transfers heat between the process fluid and the air. The process fluid heat exchange circuit has a second mode wherein the thermal energy storage transfers heat between the process fluid and the thermal energy storage and the heat exchanger transfers heat between the process fluid and the air. The method includes operating the process fluid heat exchange circuit in the second mode based at least in part upon a parameter of the air and a determination of the process fluid heat exchange circuit in the first mode being unable to provide the process fluid to the industrial process at the process fluid set temperature.

In one aspect of the present disclosure, a heat transfer apparatus is provided that includes a process fluid heat exchange circuit including a heat exchanger, an airflow generator operable to cause air to contact the heat exchanger, a thermal energy storage, and a mechanical cooler. The process fluid heat exchange circuit has a plurality of modes including a first mode wherein the heat exchanger is operable to transfer heat between a process fluid and the air and a second mode wherein the heat exchanger is operable to transfer heat between the process fluid and the air and the mechanical cooler is operable to remove heat from the process fluid. The plurality of modes further includes a third mode wherein the heat exchanger is operable to transfer heat between the process fluid and the air and the thermal energy storage is operable to remove heat from the process fluid and a fourth mode wherein the heat exchanger is operable to transfer heat between the process fluid and the air, the mechanical cooler is operable to remove heat from the process fluid, and the thermal energy storage is operable to remove heat from the process fluid. The heat transfer apparatus further includes a controller configured to operate the process fluid heat exchange circuit in one of the plurality of modes based at least in part upon a determination of a thermal duty of the heat transfer apparatus. In this manner, the controller may operate the process fluid heat exchange circuit in various configurations based at least in part upon the thermal duty which provides flexibility in tuning the heat transfer apparatus to efficiently remove heat from the process fluid.

In another aspect of the present disclosure, a heat transfer apparatus is provided including an air inlet, an air outlet, and a process fluid cooling system for cooling a process fluid. The process fluid cooling system includes a fan assembly to cause air to travel from the air inlet to the air outlet, a dehumidifier having a dehumidification mode wherein the dehumidifier removes water from the air and a bypass mode wherein the dehumidifier removes less water from the air than when the dehumidifier is in the dehumidification mode, and an adiabatic precooler having a precooler mode wherein the adiabatic precooler lowers the dry bulb temperature of the air and a standby mode wherein the adiabatic precooler lowers the dry bulb temperature of the air less than when the adiabatic precooler is in the precooler mode. The heat transfer apparatus further includes a heat exchanger that receives the process fluid and is downstream of the dehumidifier and the adiabatic precooler. The process fluid cooling system has a first mode wherein the dehumidifier is in the dehumidification mode and the adiabatic precooler is in the precooler mode, a second mode wherein the dehumidifier is in the bypass mode and the adiabatic precooler is in the precooler mode, and a third mode wherein the dehumidifier is in the bypass mode and the adiabatic precooler is in the standby mode. In this manner, the dehumidifier and the adiabatic precooler may be selectively operated to satisfy an operating criterion for the heat transfer apparatus such as providing a process fluid at a process fluid set temperature, satisfying a heat transfer load, minimizing energy consumption, and/or minimizing water consumption. Further, the heat transfer apparatus may include a water recovery system to recover water removed from the air by the dehumidifier. The recovered water may be utilized by the heat transfer apparatus as make-up water for the adiabatic precooler as one example.

The present disclosure also provides a heat transfer apparatus having a heat exchanger for cooling a process fluid, the heat exchanger comprising a liquid distribution system, and a fan operable to cause air to move relative to the heat exchanger. The heat exchanger has a wet mode wherein the liquid distribution system distributes liquid and a dry mode wherein the liquid distribution system distributes less liquid than in the wet mode. The heat transfer apparatus further includes a thermal energy storage having a heat transfer mode wherein the thermal energy storage removes heat from the process fluid and a bypass mode wherein the thermal energy storage removes less heat from the process fluid than when the thermal energy storage is in the heat transfer mode. The heat transfer apparatus further includes a controller configured to receive either a request to minimize water consumption or a request to minimize energy consumption and determine a thermal duty for the heat transfer apparatus from a plurality of thermal duties including a lower thermal duty, an intermediate thermal duty, and a higher thermal duty. In response to receiving the request to minimize water consumption, the controller is configured to operate the heat exchanger in the dry mode and the thermal energy storage in the bypass mode based at least in part upon the thermal duty being the lower thermal duty; operate the heat exchanger in the dry mode and the thermal energy storage in the heat transfer mode based at least in part upon the thermal duty being the intermediate thermal duty; and operate the heat exchanger in the wet mode and the thermal energy storage in the heat transfer mode based at least in part upon the thermal duty being the higher thermal duty. In response to receiving the request to minimize energy consumption, the controller is configured to operate the heat exchanger in the wet mode and the thermal energy storage in the bypass mode based at least in part upon the thermal duty being the lower thermal duty; and operate the heat exchanger in the wet mode and the thermal energy storage in the heat transfer mode based at least in part upon the thermal duty being the higher thermal duty. The controller may thereby operate components of the heat transfer apparatus in different modes depending on the thermal duty and the request to minimize water or energy consumption, which permits accurate and efficient operation of the heat transfer apparatus to provide a requested process fluid set temperature, for example.

With reference to, a heat transfer apparatusaccording to a first approach is provided. The heat transfer apparatushas an outer structure such as a housing, one or more air inletsand one or more air outlets. The heat transfer apparatushas a heat exchangerfor transferring heat between the process fluid and the air moving from the air inletsto the air outlet. The heat exchangermay utilize various air/process fluid flow configurations, such as cross-flow, counter flow, parallel flow, or a combination thereof. The heat transfer apparatusfurther includes a thermal energy storage (TES) such as a phase change material (PCM) tankand a mechanical cooler, such as a heat pump or chiller, for providing additional heat transfer for the process fluid. The PCM in the PCM tankmay have a fixed or variable freezing temperature. The heat exchangerincludes an adiabatic precoolerhaving a precooling padand an indirect heat exchanger such as a fluid cooling coil. The heat transfer apparatushas an air flow generator such as one or more fansthat are operable to cause air flow from the air inlets, across the precooling padsand fluid cooling coils, and out from the air outlet. The one or more fansmay be fixed or variable speed fans. The PCM tankand chillerprovide trim cooling as needed to satisfy a cooling load requirement while permitting the fan, adiabatic precooler, and indirect heat exchangerto be sized for less than peak cooling loads which reduces water consumption and/or energy consumption for off-peak cooling loads. The heat transfer apparatusmay thereby satisfy a peak cooling load or requested process fluid set temperature for an industrial process at a particular geographic location even on the hottest days of the year. Further, the heat transfer apparatusis operable to either minimize water consumption or energy consumption while satisfying cooling loads throughout the year.

Regarding, a more detailed schematic representation of the heat transfer apparatusis provided. The heat transfer apparatusincludes a process fluid inletto receive process fluid, such as a water or water/glycol mixture, from an industrial process such as a computer datacenter. In one embodiment, multiple heat transfer apparatusesmay be arranged in parallel such that the process fluid inletreceives process fluid from an upstream heat transfer apparatus. The process fluid received at process fluid inletmay be a liquid, a gas, or a liquid/gas mixture. The heat transfer apparatushas a process fluid outletfor returning process fluid to the industrial process, or to a downstream heat transfer apparatus. The heat transfer apparatusmay be operated to cool or heat the process fluid received at the process fluid inletas desired for a particular embodiment.

The heat transfer apparatushas a controllerwith a memorythat is a non-transitory computer readable medium for storing instructions to operate the heat transfer apparatus. The controllerhas a processorto perform the instructions stored in the memoryand control the heat transfer apparatus. The controllerfurther includes a communication circuitryfor communicating with a remote device, such as a HVAC system controller of a building. The communication circuitryreceives a process fluid variable, such as at least one of temperature, pressure, and flow rate, that the remote device has requested the heat apparatusto provide. The processorstores the process fluid variable in a memoryand operates the heat transfer apparatusto provide process fluid at the process fluid outletthat satisfies the process fluid variable. The communication circuitrymay receive other data from the remote device as well as transmit data to the remote device, such as air temperature and/or pressure; process fluid temperature, flow rate, and/or pressure; and/or component status data.

The adiabatic precoolerincludes an evaporative liquid distribution systemconfigured to distribute evaporative liquid, such as water, onto the precooling pad. The evaporative liquid distribution systemincludes a sumpto collect evaporative liquid from the precooling padand a pumpto pump evaporative liquid from the sumpto a liquid distributor, such as a spray nozzle, of the evaporative liquid distribution systemto distribute evaporative liquid onto the precooling pad. The evaporative liquid distribution systemfurther includes a makeup valveto permit water to be added to the sumpto compensate for evaporation of evaporative liquid, a liquid level sensorto detect the level of the evaporative liquid in the sump, a drain valvefor draining the sump, and a conductivity sensorfor monitoring one or more variables of the evaporative liquid in the sump.

The chillermay take different forms, such as a refrigerant-based chiller, a solid state chiller (e.g., electrocaloric, magnetocaloric, thermoelastic), or a gas-based chiller (reverse Brayton cycle) as some examples. In the embodiment of, the chilleris refrigerant-based chiller and includes a condenser, an evaporator, a compressor, and an expansion valve.

The heat transfer apparatushas a process fluid distribution systemfor directing the flow of process fluid between the components of the heat transfer apparatus. The process fluid distribution systemmay include one or more bypass pump(s), throttling valve(s), and bypass valve(s). A given valve may function either as a bypass valve or a throttling valve depending on the mode of the heat transfer apparatus, as discussed in greater detail below.

The PCM tankincludes a phase change material, such as ice or another phase change material having a melting temperature above 32° F. and a heat exchangerfor exchanging heat between the phase change materialand the process fluid. The phase change materialmay include ice, paraffin waxes, non-paraffin organics, hydrated salts, or metallics as some examples. The PCM tankfurther includes a drain valvefor emptying the PCM tank, a flow valveto fill the PCM tank, an air pressure sensorfor detecting air pressure in the PCM tank, an air release valveto release air pressure from the PCM tankwhen the air pressure exceeds a predetermined threshold, and a PCM charge sensor. An example of the PCM charge sensoris a liquid level sensor for PCM having different solid and liquid densities. Another example of the PCM charge sensoris one or more temperature probes at different locations on the PCM tank. The PCM tankfurther includes a humidity control systemfor detecting humidity within the PCM tank. The humidity control systemmay include a relative humidity sensorand a humidity control devicesuch as a dehumidifier.

The PCM tankhas an air distribution systemfor blowing air into the PCM tankto agitate the liquid PCM and promote faster and more even melting and/or freezing of the PCM. The air distribution systemdirects air into the PCM at the bottom of the PCM tankand the air agitates the PCM as the air rises in the PCM tank. To provide this functionality, the air distribution systemmay include an air pump, check valve, relative humidity sensor, and a humidity control device such as a vent as shown in.

The heat transfer apparatusof the first approach may take various forms. With reference to, a heat transfer apparatusis provided that is a first example of the heat transfer apparatus. The heat transfer apparatusincludes a process fluid heat exchange circuitoperable to receive a process fluid from a cooling load, cool the process fluid to achieve a requested process fluid variable such as a process fluid set temperature, and direct the cooled process fluid back to the cooling load. The heat transfer apparatushas a controllerfor operating the components of the process fluid heat exchange circuit.

The process fluid heat exchange circuitincludes a heat exchangerhaving an adiabatic precoolerand an indirect heat exchanger such as a fluid cooling coil. The adiabatic precoolerhas a precooling padand an evaporative liquid distribution systemfor distributing evaporative liquid onto the precooling pad. The evaporative liquid distribution systemincludes a sumpfor collecting evaporative liquid from the precooling padand a sump pumpoperable to pump the evaporative liquid from the sumpto the precooling pad.

The heat transfer apparatusincludes a fanto generate air flow across the precooling padand the fluid cooling coil. The adiabatic precoolerreduces the dry bulb temperature of the air before the air reaches the fluid cooling coilwhich improves the efficiency of heat transfer between the air and a fluid cooling coil. The heat transfer apparatusfurther includes a chillerhaving a condenserand an evaporatorthat are configured to transfer heat to or from a process fluid from the cooling load. The heat transfer apparatushas a PCM tankand a closed-loop pumpthat is used to recharge the PCM tankas discussed in greater detail below. The heat transfer apparatusis organized as a base modulethat may be added to other base modules in series or parallel to provide a desired amount of cooling capacity for the cooling load. The components of the heat transfer apparatusmay be within a single outer structure or may be arranged in multiple outer structures as desired for a particular embodiment.

Regarding, a methodis provided for operating the heat transfer apparatus. The methodis provided as a chart organized by thermal dutythat increases from an easythermal duty to a hardthermal duty. The thermal duty of the heat transfer apparatusmay be determined by one or variables, such as ambient air temperature (e.g., wet bulb and/or dry bulb), ambient air humidity, the temperature and/or humidity of air inside of the heat transfer apparatus, process fluid set temperature, process fluid pressure, process fluid flow rate, time of day, season, or a combination thereof. The methodhas logicthat facilitates changing of the heat transfer apparatusbetween operating modesas the thermal dutychanges. In one embodiment, the controllerprogresses from an “easier” operating modeto a “harder” operating modein response to the heat transfer apparatusin the “easier” operating modebeing unable to satisfy a process fluid set temperature requested by, for example, an HVAC system controller.

The methodfurther includes variablesof components of the heat transfer apparatusthat vary as the heat transfer apparatuschanges between the operating modes. In method, the controllerhas received a request to minimize water consumption such that the methodis representative of a water saving sequence option. The request may be received from a remote device via the communication circuitryor may be determined by the controllerbased upon data available to the controllersuch as an ambient air variable, a process fluid variable, a variable indicative of a state of a component of the heat transfer apparatus, or a combination thereof. Further, the PCM tankis capable of discharging in the method.

More specifically, the operating modesinclude a dry cooling modethat may be the default mode that the controllerbegins with in response to a request for the heat transfer apparatusto provide a process fluid to the cooling loadat a process fluid set temperature. In the dry cooling mode, the variablesinclude a fan status, a sump pump status, a statusof whether process fluid is flowing through the fluid cooling coil, a statusof whether the evaporatorand PCM tankare bypassed, a statusof the chiller, a statusof the closed-loop pump, and a statusof whether process fluid is flowing through the condenserof the chiller. The variablesfurther include a statusof whether the process fluid is flowing through the evaporatorof the chiller, a statusof whether the process fluid is flowing through the PCM tank, a statusof the charge of the PCM tank, and a statusregarding the mode of the PCM tank. The statusindicates whether the PCM tankis available to discharge or charge during the different operating modesof the method.

In the dry cooling mode, the fanis on, the sump pumpis off, the process fluid flows through the fluid cooling coil, and the evaporatorof the chillerand the PCM tankare fully bypassed. Further, in the dry cooling mode, the chilleris off, the closed-loop pumpis off, the process fluid bypasses the condenserof the chiller, and the process fluid is unable to flow through the evaporatorof the chiller. Still further, in the dry cooling mode, the process fluid bypasses the PCM tankand the PCM tankhas a charge of greater than or equal to 0%.

As the thermal dutygets harder or the thermal load increases, the controllerchanges from the dry cooling modeto another operating modebased upon a determinationof whether the PCM tankhas a charge of greater than a predetermined minimum threshold such as 10%, 5%, or 0%. In the method, the predetermined minimum threshold is 0%.

If the PCM tankhas a charge of greater than the predetermined minimum threshold, the controllerenters a dry cooling and phase change material mode. In the dry cooling and phase change material mode, a portion of the process fluid enters the evaporatorof the chillerand the PCM tankand a portion of the process fluid bypasses the evaporatorand the PCM tankas indicated by reference numeralsandin method. Further, in the dry cooling and phase change material mode, the PCM tankis in a discharge mode as indicated by reference numeral.

If, however, the controllerdeterminesthat the PCM tank charge is not greater than the predetermined minimum threshold, the controllermay skip the dry cooling and PCM modeand advance to a dry cooling chiller mode. The dry cooling and chiller modepermits greater cooling capacity than the dry cooling mode. In the dry cooling and chiller mode, a portion of the process fluid flows through the condenserand the evaporatorof the chilleras shown by reference numerals,and the chilleris on as shown by reference numeral. Because the PCM tankhas a charge of 0%, the process fluid does not flow through the PCM tankas shown by reference numeral.

If the thermal dutycontinues to increase when the heat transfer apparatusis in the dry cooling and chiller mode, the controllerdetermineswhether the PCM tank charge is greater than 0%. If the PCM tank charge is greater than 0%, the controllerchanges the heat transfer apparatusto the dry cooling, chiller, and PCM modeto accommodate the increase in thermal duty. As shown in, the controllermay enter the dry cooling, chiller, and PCM modeafter being in the dry cooling and chiller modefrom the dry cooling and chiller modewhen the tank charge is 0% or, alternatively, the controllermay enter the dry cooling, chiller, and PCM modefrom the dry cooling and PCM modeif the charge of the PCM tankis greater than zero. In the dry cooling, chiller, and PCM mode, a portion of the process fluid flows through the chiller condenserand chiller evaporatoras shown by reference numerals,and the chilleris on as shown by reference numeral. Because the PCM tankhas a charge greater than zero, the process fluid is directed through the PCM tankas shown by reference numeralwhich cools the process fluid and the PCM tankis in a discharge mode as shown by reference numeral.

The controllermay change the operation of the heat transfer apparatusfrom the dry cooling, chiller, and PCM modeto an adiabatic cooling and PCM modeupon the controllerdeterminingthat the PCM tank charge is greater than 0% and the thermal dutycontinuing to increase. In the adiabatic cooling and PCM mode, the sump pumpis on as shown by reference numeralto pump the evaporative liquid to the precooling pad. In the adiabatic cooling PCM mode, the chilleris off as shown by reference numeraland the process fluid does not flow through the chiller condenseror the chiller evaporatoras shown by reference numerals,. The process fluid flows through the PCM tankas shown by reference numeraland the PCM tankis in the discharge modeto remove heat from the process fluid.

The methodincludes the controllerchanging the heat transfer apparatusfrom the adiabatic cooling and PCM modeto an adiabatic cooling and chiller modein response to the controllerdeterminingthe PCM tankhas a charge greater than 0% and the thermal dutycontinuing to increase. In the adiabatic cooling and chiller mode, the sump pumpis on as shown by reference numeralto wet the precooling padand decrease the dry bulb temperature of air in the heat transfer apparatusbefore the air reaches the fluid cooling coil. The chilleris on and at least a portion of the process fluid flows through the chiller condenserand chiller evaporatoras shown by reference numerals,,. Because the PCM tankhas a charge of 0% at step, the process fluid does not flow through the PCM tankin the adiabatic cooling and chiller modeas shown by reference numeral.

The heat transfer apparatusmay enter the adiabatic cooling and chiller modefrom the adiabatic cooling and PCM modeif the PCM tank has a charge of 0%. Alternatively, the heat transfer apparatusmay enter the adiabatic cooling and chiller modefrom the dry cooling and chiller modeor dry cooling, chiller, and PCM modeif the controllerdetermines the PCM tankhas a charge of 0% either at stepor, and the thermal dutycontinues to increase.

The controllermay reconfigure the heat transfer apparatusfrom the adiabatic cooling and PCM modeto an adiabatic cooling, chiller, and PCM modein response to the controllerdeterminingthat the PCM tankhas a charge greater than 0% and the thermal dutyincreasing to the hardlevel. In the adiabatic cooling, chiller, and PCM mode, the sump pumpis on as shown by reference numeral, the chilleris on as shown by reference numeral, at least a portion of the process fluid flows through the chiller condenserand the chiller evaporatoras shown by reference numerals,, and the process fluid flows through the PCM tankas shown by reference numeral. The PCM tankis in a discharge mode as shown by reference numeraland removes heat from the process fluid.

The controllermay advance through the operating modesaccording to the logicas the thermal dutyincreases or decreases. Alternatively, the controllermay hop from one operating modeto another operating mode (e.g., modeto modeor vice versa) in response to a sudden change in the thermal dutyplaced on the heat transfer apparatus.

With reference to, the controllermay utilize a methodin response to receiving a request to minimize energy consumption and the PCM tankbeing capable of discharging to provide trim cooling. The methodincludes operating modesthat the controllermay advance through as a thermal dutychanges from an initial or easylevel to a maximum or hardlevel. The methodis similar in many respects to the method. One difference is that the methodutilizes adiabatic cooling during modes,,,to limit energy consumption.

With reference to, the controller may utilize a methodin response to the controllerreceiving a request to minimize water consumption and the PCM tankis capable of being charged. The methodincludes operating modesthat the controllerprogresses through as the thermal dutychanges. The methodis similar in many respects to the methoddiscussed above and includes variablesthat vary as the controllerprogresses through the modes. One difference between methodsandis that the modesinclude a dry cooling closed-loop chiller modewherein the process fluid does not flow through the chiller evaporatoror the PCM tankas shown by reference numerals,. Instead, a secondary process fluid, which may be the same or different than the process fluid flowing through the fluid cooling coil, is circulated by the closed-loop pumpas shown by the reference numeral. The closed-loop pumppumps the secondary process fluid between the chiller evaporator, which cools the secondary process fluid, to the PCM tankto cool the phase change material in the PCM tankand charge the PCM tank. The process fluid flows through the fluid cooling coilduring operating modeto satisfy the thermal load placed on the heat transfer apparatus.

Likewise, in the adiabatic cooling and closed loop chiller mode, the process fluid does not flow through the chiller evaporatorand PCM tankas shown by reference numerals,. Instead, a secondary process fluid is circulated by the closed-loop pumpto permit the chiller evaporatorand the secondary process fluid to remove heat from the PCM tankand charge the PCM tank. In the adiabatic cooling and closed loop chiller mode, the process fluid is cooled via the fluid cooling coiland the adiabatic precoolerprecooling the air upstream of the fluid cooling coil.

The operating modesof methodinclude a dry cooling and chiller modewherein the chilleroperates and process fluid flows through the chiller evaporatorto be cooled as shown by reference numeral. Further, in dry cooling and chiller mode, a portion of the cooled process fluid flows through the PCM tankto charge the PCM tankas shown by reference numeral.

The operating modesinclude an adiabatic cooling modewherein the chilleris off. However, in the adiabatic cooling mode, process fluid cooled by the fluid cooling coilflows to the PCM tankto charge the PCM tankas shown by reference numeral. The operating modesfurther include an adiabatic cooling and chiller modewherein process fluid cooled by the fluid cooling coiland the chiller evaporatoris routed to the PCM tankto charge the PCM tankas shown by reference numeral.

With reference to, the controllermay utilize a methodin response to receiving a request to minimize energy consumption and the PCM tankis capable of being charged. The methodincludes operating modesthat the controllerprogresses through in response to a thermal dutyfor the heat transfer apparatusincreasing.

With reference to, a heat transfer apparatusis provided that is a second example of the heat transfer apparatusdiscussed above. The heat transfer apparatushas a process fluid heat exchange circuitthat receives process fluid from a cooling loadat an elevated temperature and cools the process fluid so that the process fluid heat exchange circuitcan return cooled process fluid to the cooling loadat a process fluid set temperature, for example. The heat transfer apparatusis similar in many respects to the heat transfer apparatusexcept that the heat transfer apparatuslacks a closed-loop pump and associated valving for circulating a secondary process fluid in a closed-loop to recharge a PCM tank. The heat transfer apparatusincludes an adiabatic precoolerhaving an evaporative liquid distribution systemfor distributing evaporative liquid onto a precooling padand a pumpof a sumpto pump collected evaporative liquid to the precooling pad. The heat transfer apparatusfurther includes a fluid cooling coil, a fan, a chiller, and a PCM tank.

Regarding, a methodis provided that a controllerof the heat transfer apparatusmay use in response to receiving a request to minimize water consumption and the PCM tankbeing capable of discharging. The methodincludes modesthat the controllerprogresses through according to logicas a thermal dutyvaries between an initial or easylevel and a maximum or hardlevel. The methodincludes variablesindicative of the state of the components of the heat transfer apparatusthat change throughout the different modes.

Regarding, a methodis provided that the controllermay implement in response to receiving a request to minimize energy consumption and the PCM tankbeing capable of discharging. The methodincludes modesthat the controllerprogresses through according to logicas a thermal dutyof the heat transfer apparatuschanges. The methodincludes variablesfor the components of the heat transfer apparatusthat vary according to the different operating modes.

With reference to, a methodis provided that the controllermay utilize in response to receiving a request to minimize water consumption and the PCM tankbeing capable of being charged. The methodhas modesthat the controllerprogresses through as a thermal dutyof the heat transfer apparatuschanges. The methodhas variablesof components of the heat transfer apparatusthat vary according to the different modes. One difference between the methodsandis that the methodcharges the PCM tankusing the process fluid that is received from a cooling loadrather than utilizing a closed-loop circulation of secondary process fluid. In this manner, the cooling provided by the fluid cooling coiland/or chilleris used to both cool the process fluid and to charge the PCM tank. The difference in operation is due to the lack of the closed-loop pump in the heat transfer apparatus.

Regarding, a methodis provided that the controllermay implement in response to receiving a request to minimize energy consumption and the PCM tankbeing capable of being charged. The methodincludes operating modesthat the controllerswitches between as a thermal dutyof the heat transfer apparatuschanges. The methodincludes variablesof the components of the heat transfer apparatusthat vary according to the different modes. In the method, the PCM tankis charged using the process fluid communicated with the cooling loadrather than a closed-loop charging operation as in the methoddiscussed above.

With reference to, a heat transfer apparatusis provided that is a third example of the heat transfer apparatusdiscussed above. The heat transfer apparatusis similar in many respects to the heat transfer apparatusdiscussed above. The heat transfer apparatushas a process fluid heat exchange circuitthat is operable in different modes to cool process fluid from a cooling loadand provide a supply of process fluid to the cooling loadat a requested process fluid set temperature, for example.

The heat transfer apparatushas a secondary closed-loop pumpand valves,to facilitate charging of a PCM tankas discussed in greater detail below. The heat transfer apparatusincludes an adiabatic precoolerhaving a precooling pad, a sumpand a pumpto pump collected evaporative liquid to the precooling pad. The heat transfer apparatusfurther includes a fluid cooling coil, a fan, and a chillerhaving a condenserand an evaporator. The fanis operable to draw airacross a precooling padand the fluid cooling coil. The heat transfer apparatusincludes a primary closed-loop pumpand valves,. The heat transfer apparatushas a controllerfor operating the components of the heat transfer apparatusin different modes.